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Calibration of the Advanced Virgo gravitational wave detector during the Observing Run O3

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The first joint observation in August 2017 of gravitational waves coming from a neutron star inspiral and a gamma ray burst, followed by an optical signal, opened a new chapter of astronomy. Besides confirming binary neutron star mergers as progenitors of short gamma ray bursts, new kinds of measurements have been made, from General Relativity tests to independent determination of the Hubble constant, with a precision of the order of 15%.

The ongoing work of improving the sensitivity of the LIGO and Virgo detectors should increase the number of observed sources, improving the results and opening new opportunities. For the next few years, year-long observation periods will alternate with upgrades and commissioning periods. The next Observing Run, O3, will start beginning 2019. For every Observing Run, an important detector calibration activity is needed to reconstruct the gravitational wave signal from various signals measured within the interferometer. Having more and more detections in the coming years, the precision of the detector calibration and the precision of the gravitational wave signal reconstruction will need to be better controlled.

The training period being at the beginning of the LIGO-Virgo Observing Run O3, the work will be focused on one of the following topics (depending on the period and duration) : • calibration of the Advanced Virgo detector using one out of three independent methods : ◦ the “standard” method, ◦ a method based on an auxiliary laser to move an interferometer mirror via radiation pressure (photon calibrator), ◦ a method using a rotating mass to move en interferometer mirror via variation of the local gravitational field (Newtonian calibrator). • Reconstruction of the Virgo gravitational wave signal used for the LIGO-Virgo data analysis and study of astrophysical sources.

Supervisor : Loïc Rolland (

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